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Gewählte Doctoral Thesis:

Axel Maximilian Rindler (2019): THE SIGNIFICANCE OF BOND REGION MICROMECHANICS ON THE MOISTURE RELATED DIMENSIONAL STABILITY OF THIN WOODEN MULTI-LAYERED PANELS.
Doctoral Thesis - Institut für Holztechnologie und Nachwachsende Rohstoffe, BOKU-Universität für Bodenkultur, pp 107. UB BOKU obvsg

Data Source: ZID Abstracts
Abstract:
Panel warping is a deformation without the influence of external mechanical loads and it is a challenging issue when engineering different materials to multi-layered wood-based panels. Beside the moisture-induced swelling and shrinking of wooden adherends, the adhesive zone, where occurring stresses for the adherends are expected to be compensated, might play a key role in the deformation behaviour of thin multi-layered panels. An adhesive joint exhibits different relevant bond regions that can reveal different moisture-related mechanical properties. The single regions were investigated by means of quasi-static nanoindentation under an environmentally controllable testing atmosphere to obtain their elastic, plastic and viscoelastic humidity dependent behaviour. Therefore, spruce (Picea abies) lamellas were adhesively bonded by different adhesive systems used in the furniture and flooring industry (emulsion polymer isocyanate, polyvinyl acetate, urea formaldehyde and ultra-low emitting formaldehyde amino adhesive) under laboratory conditions. Beside the micromechanical properties of the single components, the contribution of the pure adhesive zone to the macromechanical warping behaviour of thin bi-layers (Picea abies and high-density fibreboard) with identical layer geometries was analysed under changing relative humidities with a high precision laser distance detector. Additionally to the already mentioned wood adhesive systems polyurethane was used for the bi-layer bonding. In general, all adhesives respond differently to changing relative humidities, while the wood cells were less affected by the applied humidity levels. This higher sensitivity of the adhesives could also be detected regarding the warping intensity of thin bi-layers, where a differentiation between the two adhesive groups was observed. As a result, stiff and rigid adhesive systems tend to give stronger warping signals compared to more flexible ones.

Betreuer: Konnerth Johannes
1. Berater: Gindl-Altmutter Wolfgang
2. Berater: Hansmann Christian

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